SM-J727P unlock done, but SIM not valid

Please check whether GSM/(E)GPRS/WCDMA GCF is enabled in your phone:


Open hidden menu. There are two ways of doing it:
1) Run the following command via ADB:
adb shell su -c "am broadcast -a android.provider.Telephony.SECRET_CODE -d android_secret_code://IOTHIDDENMENU"

2) Perform the following actions:
1. Dial *#0011# and in the service menu do the following.
2. Click "Menu" then "Key input" then input Q then press "Ok".
3. Click "Menu" then "Back".
4. Click "Menu" then "Key input" then input 0000 then click "Ok".


After these steps Hidden menu should open. In Hidden menu, depending on available options, try to do the following:
I.
Press UMTS
Press DEBUG SCREEN
Press PHONE CONTROL
Press NETWORK CONTROL
Set GCF to ON

II.
(optional) TestMode Menu
Press [2] UE SETTING & INFO
Press [1] SETTINGS
Press [1] PROTOCOL
Press [4] GCF
Set [1] GSM/(E)GPRS/WCDMA GCF to ON


After these actions go to Settings -> Mobile Networks and Set Network Mode to Automatic, or GSM.